With few exceptions, aquatic life cannot survive outside a pH range of 5 – 9. Environmental monitoring systems use pH measurements to indicate whether pollution or natural factors, such as algae blooms, acid rain, or storm events, are impacting water sources. pH measurement may be the first signal to alert to potential problems in environmental waters. Environmental monitoring applications measure pH in the field or as grab samples in a lab. Remote stations require multiparameter sondes that continuously measure pH, log data, and transmit wirelessly. Low levels of drift reduce maintenance that is costly and inconvenient. Excessive drift and other challenges can be mitigated with the optimal sensor design, in particular the reference junction design, housing material, and sensing chemistry.